The present invention relates to a method and a device for improving the efficiency of a heat generator, e.g. a heat pump.
Heat generators of the heat pump type function in a conventional manner by passing a medium, e.g. water, air or similar medium, through an evaporator, the heat emitted being used to evaporate a refrigerant which, once its temperature and pressure have been raised, condenses in a condensor thereby transferring heat to a second medium-the medium to be heated. The efficiency or coefficient of performance (COP) of such a process depends on the difference in temperature between the evaporator and the condensor and decreases the greater that difference becomes. This means that the efficiency or COP decreases considerably with drops in the temperature of the first medium from which heat is extracted.
The quantities of the heat source medium required for heating purposes in the process described are so large that only heat sources such as those found in nature, e.g. water or atmospheric air can be used as heat source media for normal operations. Although it is possible to use water as a source of heat as mentioned above, for the sake of simplicity the following description refers to atmospheric air as the heat source medium.
The decrease in the COP described above means that when outside air is used as a heat source the COP will be lowest at low outdoor temperatures-just when the heat is most needed. In known applications of the process the COP becomes greatly reduced even at an outdoor temperature of 0.degree. C. although even colder air contains considerable amounts of heat. Additional heat must therefore be supplied at temperatures below freezing and known applications of the process are economical only down to outdoor temperatures of -5.degree. C.
Therefore the main purpose of the present invention is to provide a method of improving the efficiency of a heat generator of the type described above so that it can be used with low-temperature source media without the necessity of providing additional heating.
This is achieved by the method and device the characteristics of which are contained in the following patent claims.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.